A coke plant which manufacturers coke from coal for subsequent use in blast furnaces or foundries for making iron therefrom employs one or more coke oven batteries. A coke oven battery is a bank of coke ovens positioned side by side. A coke oven battery can contain a fairly substantial number of coke ovens, spanning a length of several hundred feet.
One side of the coke oven battery is known as the "pusher" side, while the opposite side of the coke oven battery is known as the "door" or "coke" side. On the pusher side, there is a set of railroad type rails or tracks running the length of the battery. Along this set of rails or tracks there rides what is known as a "pusher side machine" or simply "pusher machine". This pusher machine can weigh on the order of 60 to 220 tons, and carries a variety of equipment which is used in conjunction with the coke oven battery. The pusher machine normally incorporates a number of pieces of functional equipment for use in servicing the ovens, including a door extractor for removing and reattaching an oven door to its oven, a door cleaner for cleaning foreign material from the oven door, an oven jamb cleaner for cleaning foreign material from the oven jamb, a pusher ram for pushing the coke through the oven and out the opposite door, and a leveler for insertion through a separate leveler door at the upper end of the coke oven door for levelling the coal loaded from above into the oven.
The opposite side of the coke oven battery, known as the "door side" "coke side" or "back side" similarly includes a set of rails or tracks, with a somewhat smaller "coke side machine" or simply "coke machine" or "door machine" that rolls therealong. This door machine can weigh on the order of 40 to 110 tons. The door machine similarly includes a door extractor, a door cleaner and a jamb cleaner, but includes no pusher ram or leveler. The door machine includes a coke guide which is a rectangularly cross-sectioned chute used for directing the coke from the coke oven over and across the set of rails or tracks and into one or more rail cargo cars known as "hot cars".
In order to utilize the various pieces of equipment on either the pusher machine or door machine in conjunction with a selected oven, the piece of equipment carried by the machine must be aligned with the vertical centerline axis of symmetry of the selected oven which is to be serviced. Positioning the equipment carried by the machine so that its vertical centerline axis of symmetry is aligned with that of the selected oven is known as placing the machine or equipment "on spot".
Some coke plants still use the visual method whereby the operator looks across a sight in the cab to line up on a mark on a buckstay or other structure. Others use a hydraulic cylinder mounted on the door or pusher machine with a receptacle mounted on buckstays or other structures and the operator extends the cylinder shaft into the receptacle having a limit switch to signal success. Some coke plants have tried laser spotting systems but not very successfully. The laser fires a beam to a mark on a buckstay.
Another type of completely manual system for placing the functional equipment of the machine "on spot" has been developed and marketed by the assignee of the present invention. In that spotting system, the pusher or door machine has installed on the top thereof a sprocket driven 500 count encoder/pulse generator having a high speed count/pulse module. An encoder chain is mounted from the face of the battery, e.g. the hot rail outriggers to span the length of the coke oven battery, and is positioned to mesh with the sprocket driven encoder as the machine travels along the tracks. This system further includes a programmable logic controller having a minimum of 6 K of memory, 16 bits of discrete inputs, 16 bits of discrete outputs, a chassis, a power supply for the chassis, a Panelview display monitor for operator input and display output, and a limit switch for resetting the encoder at the zero location all purchased from Allen Bradley. Of course other suppliers could supply equivalent equipment. As the machine travels down the tracks, the encoder sprocket is driven by the encoder chain. The computer is programmed with the position along the chain corresponding to the position of the centerline axis of each oven; therefore for a particular position of the machine along the chain and hence tracks the computer knows the distance between the machine, and hence the functional equipment carried by the machine, and the centerline of any selected oven. Consequently, via the Panelview display, the computer will indicate to an operator the direction in which the machine must travel in order to align the selected piece of equipment carried by the machine with the selected oven. The operator energizes the travel controller by pushing the appropriate button or otherwise activating the appropriate control on the Panelview display to move the machine in one direction along the rails, or reverses the travel controller to move the machine in the other direction along the rails. The Panelview display continues to indicate the direction in which the car is required to be moved to align the piece of equipment with the selected oven. When the machine gets near the selected oven the operator slows the machine, and then gradually moves the machine on spot using the manually operated travel controller. Should the operator cause the machine to overshoot the on spot position, the Panelview display simply indicates that the machine must then be moved in the opposite direction. The operator so jogs or jockeys the machine back and forth using the manual travel controller until the Panelview display indicates the precise on spot position.
The resolution of the sprocket driven encoder in combination with the chain is on the order of plus or minus 0.025 inch. However, due to the limitations of a human operator's manual dexterity in operating the travel controller, an operator is normally only able to position or spot the machine and its associated equipment within plus or minus 1/2" of the true on spot position. Consequently, via this manual type of spotting, an operator is unable to exploit the resolution of the encoder as he is normally off of true on spot by plus or minus 1/2". By being off by as much as plus or minus 1/2" the equipment carried by the pusher machine and door machine can be damaged, and can damage the coke oven door and the door jamb. For example, when replacing a door that has been extracted from its oven, a variation of plus or minus 1/2" from true on spot can greatly damage the seal of the coke oven door and/or the jamb of the coke oven itself. This damage results in downtime of the oven and costly repair is required to repair the door jamb and/or door seal. Similarly, if the jamb cleaner is off by as much as plus or minus 1/2" it likewise can become damaged and/or damage the door jamb. The same is true if the pusher ram is off by as much as plus or minus 1/2".
Damage also results to the coke oven door jamb and the coke oven door and seal due to the fact that the traditional door extractor which removes and replaces a coke oven door from and into its respective coke oven jamb cannot compensate for thermal distortion of the coke oven battery and consequential distortion of the plane of the coke oven door jamb. More particularly, the heat generated by the coke oven battery causes the upper portion of the battery to expand. When viewed from the side, the battery assumes a "V" shape, in that the plane of the door jambs on both the pusher and coke sides of the oven tilt outwardly at the top. In some instances, the top part of the jamb will project outwardly as much as 8 inches further than the bottom portion of the jamb. Similarly, when viewed from the front or back, the battery likewise assumes a "V" shape, in that the coke oven battery expands outwardly side-to-side on its ends at the top. Thus, a selected coke oven door jamb and its corresponding door may be leaning either to the left, or to the right, as viewed when facing the oven door, due to whether the particular oven is left or right of the centerline of the battery.
Such thermal distortion of the coke oven battery results in damage to doors and jambs since current door extractors do not have the capability to match the orientation of the oven jamb, and hence the door, as the oven jamb's orientation, and hence door's orientation, changes due to battery thermal expansion. More particularly, these traditional prior art door extractors have no ability to actively tilt from front-to-back to compensate for front-to-back tilting of the jamb. While in some prior art door extractors the extractor is spring mounted and will passively accommodate for some front-to-back tilting of the oven jamb, the pressure needed to overcome the spring force often is sufficient to damage the coke oven door seal.
In other prior art door extractors, while the extractor has the capability of being leaned to compensate for side-to-side leaning of the jamb, such leaning is accomplished manually. Thus, without some means of automatically controlling the lean adjustment, such adjustment has been somewhat tedious and time consuming.
Further, variations in door height have heretofore presented problems for prior art door extractors when trying to match the individual heights of each of the doors. Coke build up on the hearth plate causes such variation in door height since the door rests atop the coke laden hearth plate. The prior art door extractors, utilizing pure rotation of a door extractor arm to engage the door, are inherently inaccurate when trying to match the vertical position of the door since the point at which the arcing extractor arm contacts the door is a function of the distance between the door and door extractor, which varies because of several causes. Deviation in the vertical position of individual ovens also creates vertical positioning problems for prior art door extractors. And, variation in the vertical distance between the tracks on which the machine rides and the ovens creates differences in the relative vertical position between the extractor and individual doors.
Thus, current prior art coke oven door extractors damage coke oven doors and door seals in several ways. Because the coke oven battery and hence coke oven expansion is tilting the door forward at its upper end, the extractor, unable to compensate for this forward tilting, puts undue pressure on the top door section as it removes and reinstails the doors, thus causing seal damage. And with a door jamb and hence door which leans to one side, previous prior art door extractors lacking a lean adjustment damage the refractory plug components mounted to the backs of the doors as well as the door seals because the door extractor can only orient the door vertically, and cannot lean the door in the precise desired amount in a side-to-side direction to align the height centerline axis of the door with the height centerline axis of the oven jamb. In prior art extractors having a lean adjustment, such adjustment, being manual, is tedious and time consuming. And the lack of uniformity in relative position between a door extractor and the individual battery ovens can cause seal and door damage by prior art extractors unable to compensate for varying heights of ovens.